1. Field of the Invention
The present invention relates to an inverter microwave oven and a method for controlling the same, and more particularly to an inverter microwave oven and a method for controlling the same, wherein an inverter control unit is provided to vary a switching frequency of an inverter so as to prevent overvoltage from being applied to a magnetron during the initial operation of the microwave oven.
2. Description of the Related Art
FIG. 1 is a block diagram showing the construction of a conventional inverter microwave oven and FIG. 2 is a detailed block diagram of the conventional inverter microwave oven.
The microwave oven is generally adapted to position food in a cavity 1 and radiate electromagnetic waves to the food in the cavity 1 to heat it.
A magnetron M acts to generate the electromagnetic waves. In order to drive the magnetron M, a commercial alternating current (AC) voltage source 3 supplies a commercial AC voltage of 60 Hz to a general home, in which the microwave oven is installed, and an inverter 2 converts the commercial AC voltage from the commercial AC voltage source 3 into a high-power direct current (DC) voltage of about 3500V or more and supplies the converted DC voltage to the magnetron M.
In detail, the commercial AC voltage from the commercial AC voltage source 3 is rectified and converted into a DC voltage by a DC voltage source 4, composed of a bridge diode, and then inputted to a switching device 5. The switching device 5 performs a switching operation based on the DC voltage from the DC voltage source 4. To this end, the switching device 5 includes a plurality of switches turned on/off in response to the DC voltage from the DC voltage source 4 to generate a high-power AC voltage. This AC voltage from the switching device 5 is applied to a magnetron driver 6, which converts the AC voltage from the switching device 5 into a high-power DC voltage appropriate to the driving of the magnetron M and outputs the converted DC voltage to the magnetron M.
An inverter control unit 7 is further provided to control the switching operation of the switching device 5. The inverter control unit 7 includes a frequency generator 8 for generating a reference frequency varying with the output of the magnetron M under control of an output controller (not shown), and an inverter driver 9 for applying a switching control signal to the switching device 5 according to the frequency generated by the frequency generator 8 to control a switching frequency of the switching device 5.
However, the conventional inverter microwave oven with the above-mentioned construction has a disadvantage in that, if the frequency generated by the frequency generator is applied to the inverter driver during the initial operation of the microwave oven where there is no load on the magnetron, overvoltage is applied to the magnetron, resulting in degradation in durability of the inverter circuit.
In order to solve the above problem, it may be intended to raise the switching frequency of the inverter during the initial operation of the microwave oven. In this case, however, the drive voltage to the magnetron may become too low in level, causing a faulty operation of the magnetron.